European Journal of Radiology 36 (2000) 81 – 85 Colonography using multislice CT Patrik Rogalla a, *, Noga Meiri a , Jens C. Ru ¨ ckert b , Bernd Hamm a a Department of Radiology, Charite ´ Hospital, Humboldt -Uniersita ¨t zu Berlin, Schumannstr. 20 /21, 10098 Berlin, Germany b Department of Surgery, Charite ´ Hospital, Humboldt -Uniersita ¨t zu Berlin, Schumannstr. 20 /21, 10098 Berlin, Germany Received 26 July 2000; received in revised form 27 July 2000; accepted 27 July 2000 Abstract Computed tomography (CT) represents the preferred imaging modality for imaging the large bowel when virtual endoscopic reconstructions are desired. Using the spiral acquisition technique, it has become possible to scan the entire abdomen within a single breathhold, however, slice thicknesses of 5 mm or more are necessary should the breathhold not last longer than 30–40 s. With the advent of multislice CT, contiguous 1-mm slices can be obtained through the entire abdomen while even shortening the breathhold to 25 – 30 s. The improved speed and spatial resolution of multislice CT results in remarkably sharp virtual reconstructions allowing detection of polyps with sizes less than 3 mm. The disadvantages must still be considered including a dataset consisting of up to 800 images representing a new challenge for postprocessing hard- and software. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Computed tomography; Multislice CT; Fibre-optic endoscopy www.elsevier.nl/locate/ejrad 1. Background Colorectal cancer represents the third most diagnosed cancer worldwide, and the second most diagnosed can- cer in industrialised Western countries [1 – 3]. In the United States, 129 000 new cases were diagnosed in 1999 [4], however, when malignant polyps are consid- ered, the true yearly incidence of colorectal cancer probably approaches 160 000 [1]. Approximately, one- half to two-thirds of all colorectal polyps are of the adenomatous type, and by the age of 50, these may be found in about 25% of the population. The incidence increases with age and the possibility of malignant transformation with size. With the fact in mind that malignant transformation is found in approximately 1% of polyps less than 1 cm in size compared with 10% of larger polyps [5,6], early detection of colorectal polyps by means of screening asymptomatic individuals who have not any risk factors (and re-evaluating who be- longs in the target group) might be regarded as one of the leading goals in health care management. Virtual colonoscopy has not yet gained widespread acceptance among radiologists or gastroenterologists. In addition, the clinical results available to date, al- though often including a correlation with flexible en- doscopy or surgery, have all been conducted with selected patient populations, whereas a true ‘screening population’ would have a lower prevalence of col- orectal cancer or adenomatous polyps. Despite the possibility to calculate sensitivities and specificities also in small populations, a low specificity for virtual en- doscopy in a screening setting would have the conse- quence that many false positive patients would have to be re-examined with flexible endoscopy. The costs in- curred by false positive tests are substantial and must be included when assessing the cost-effectiveness of virtual endoscopy. 2. Clinical performance using spiral CT In an initial assessment of sensitivity and specificity for polyps larger than 10 mm, a 75% sensitivity and a 90% specificity was reached; for polyps with a size ranging between 5 and 10 mm, a 66% sensitivity and a 63% specificity; and for polyps smaller than 5 mm, a * Corresponding author. E-mail address: rogalla@colonography.com (P. Rogalla). 0720-048X/00/$ - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S0720-048X(00)00267-9